How to be a successful pest: Lessons from the green peach aphid

IMAGE: This is a single green peach aphid Myzus persicae) feeding from a leaf.
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Credit: Andrew David (JIC)

UK Scientists, in collaboration with groups in Europe and the US, have discovered why the green peach aphid (Myzus persicae) is one of the most destructive pests to many of our most important crops. Their research will inform industry and research programmes to support pest control and aid global food security.

Unlike most plant-colonising insects, which have adapted to live on a small range of closely related plants, green peach aphids can colonise over four hundred plant species. Developing resistance to over 70 different pesticides, coupled with the ever changing climate affecting crop losses in the EU and UK, the pest wreaks havoc on crop yields.

The green peach aphid transmits over a hundred different plant viruses and this notorious insect feeds on essential crops such as oilseed rape, sugar beet, tomato and potato, as well as wild plant species, which may serve as sources of the plant viruses. An example being the Turnip yellows virus (TuYV) and related viruses, which if left uncontrolled can reduce yields of multiple crops, such as oilseed rape and sugar beet, by up to 30%, rendering some crops unprofitable in the UK.

The aphids spend winter living on host plants such as peach, apricot or plum, but in the summer months can colonise a huge range of vegetables -- from potatoes to spinach, squash, parsley and parsnip.

Generally, the insect parasites that live on a certain species are genetically very well adapted to live on just that plant. Yet, research led by the Earlham Institute (EI) and the John Innes Centre (JIC), has found that the green peach aphid foregoes this specialisation for a more flexible approach involving turning gene activity 'up' or 'down' in response to different plant hosts and environments.

Dr David Swarbreck, Group Leader at the Earlham Institute, said: "Our study has shed light on the genetic plasticity1 that allows the green peach aphid to survive so well on a multitude of plant species, giving us a greater insight into the survival strategies of one of the most challenging of crop pests."

More intriguing about the insect's strategy is that aphids can reproduce clonally -- i.e. they produce genetically identical lineages. This allows biologists to compare individual aphids with the same genetic background and see precisely what genes are more active than others in aphids living on different plant species.

By growing aphid clones on three different plant species, it was possible for the scientists to find the specific genes that were involved in colonising the different host plants. It appears that the genes responsible for helping aphids adjust to different plants are found in clusters within the genome and are rapidly increased or decreased in two days of transfer to a new host plant species.

Dr Yazhou Chen, Postdoctoral Scientist at the John Innes Centre, said: "The genes rapidly turn up or down in single aphids in just two days upon transfer to a new host plant. Given that a single aphid can produce her own offspring, and a lot of it, new aphid infestations may start with just a single aphid."

The team found that rapid changes in gene expression were vital for the green peach aphid's generalist lifestyle. Interfering with the expression of one particular gene family, cathepsin B, reduced aphid offspring production, but only on the host plant where the expression of these genes is increased.

Thomas Mathers, Postdoctoral Scientist at the Earlham Institute, said: "Surprisingly, many of the genes involved in host adjustment arose during aphid diversification and are not specific to the green peach aphid. This suggests that it may be the ability to rapidly adjust the expression of key genes in a coordinated fashion that enables generalism, rather than the presence of an expanded genomic toolbox of genes."

Professor Saskia Hogenhout at the John Innes Centre, added: "Future research is expected to reveal mechanisms involved in the amazing plasticity of the green peach aphid leading to new ways to control this notorious pest. More generally, the research will help understand how some organisms are able to adjust quickly to a broad range of environmental conditions, whereas others are pickier and go extinct more easily, research that is central given our rapidly changing environment due to, for instance, climate change."

This research project was led by the Earlham Institute (Norwich, UK) and the John Innes Centre (Norwich, UK) in collaboration with the University of East Anglia (Norwich, UK), INRA Rennes (France), University of Miami (USA) and Boyce Thomspon Institute for Plant Research (New York, USA).

This project was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the United States Department of Agriculture (USDA) and the National Institute for Food in Agriculture (NIFA), (USA).

1. The ability of one genotype to produce more than one phenotype when exposed to different environments - phenotypic plasticity allows an organism to change its phenotype in response to changes in the environment.

2. Paper DOI: 10.1186/s13059-016-1145-3 (Paper PDF available on request). Link to paper title goes live after embargo has lifted.

Formerly The Genome Analysis Centre (TGAC), the Earlham Institute is a leading research institute focusing on the development of genomics and computational biology. The Earlham Institute is based within the Norwich Research Park and is one of eight institutes that receive strategic funding from Biotechnology and Biological Science Research Council (BBSRC) -- £6.45M in 2015/2016 -- as well as support from other research funders. The Earlham Institute operates a National Capability to promote the application of genomics and bioinformatics to advance bioscience research and innovation.

The Earlham Institute offers a state of the art DNA sequencing facility, unique by its operation of multiple complementary technologies for data generation. The Institute is a UK hub for innovative bioinformatics through research, analysis and interpretation of multiple, complex data sets. It hosts one of the largest computing hardware facilities dedicated to life science research in Europe. It is also actively involved in developing novel platforms to provide access to computational tools and processing capacity for multiple academic and industrial users and promoting applications of computational Bioscience. Additionally, the Institute offers a training programme through courses and workshops, and an outreach programme targeting key stakeholders, and wider public audiences through dialogue and science communication activities.

The John Innes Centre is an independent, international centre of excellence in plant science and microbiology.
Our mission is to generate knowledge of plants and microbes through innovative research, to train scientists for the future, to apply our knowledge of nature's diversity to benefit agriculture, the environment, human health and wellbeing, and engage with policy makers and the public.

To achieve these goals we establish pioneering long-term research objectives in plant and microbial science, with a focus on genetics. These objectives include promoting the translation of research through partnerships to develop improved crops and to make new products from microbes and plants for human health and other applications. We also create new approaches, technologies and resources that enable research advances and help industry to make new products. The knowledge, resources and trained researchers we generate help global societies address important challenges including providing sufficient and affordable food, making new products for human health and industrial applications, and developing sustainable bio-based manufacturing.

This provides a fertile environment for training the next generation of plant and microbial scientists, many of whom go on to careers in industry and academia, around the world.

The John Innes Centre is strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC). In 2015-2016 the John Innes Centre received a total of £30.1 million from the BBSRC.

The John Innes Centre is also supported by the John Innes Foundation through provision of research accommodation and long term support of the Rotation PhD programme. The John Innes Centre is the winner of the BBSRC's 2013 - 2016 Excellence With Impact award.

8. About BBSRC

The Biotechnology and Biological Sciences Research Council (BBSRC) invests in world-class bioscience research and training on behalf of the UK public. Our aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.

Funded by Government, BBSRC invested over £509M in world-class bioscience in 2014-15 and is the leading funder of wheat research in the UK (over£100M investment on UK wheat research in the last 10 years). We support research and training in universities and strategically funded institutes. BBSRC research and the people we fund are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Our investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.

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